1. Field of the Invention
This invention relates to lighting devices and systems, and in particular, it relates to devices for generating high brightness multicolor light using wavelength conversion.
2. Description of the Related Art
Wavelength conversion methods that use excitation light produced by solid-state light source such as laser diodes (LDs) or light emitting diodes (LEDs) and wavelength conversion materials such as phosphors or quantum dots can produce high brightness light at wavelengths different from the wavelength of the excitation light. In conventional devices, excitation light impinges on a wavelength conversion material, which absorbs the excitation light and emits light (the converted light) at a wavelength higher than the wavelength of the excitation light. To generate light of different colors, different wavelength conversion materials are typically employed.
U.S. Pat. No. 7,547,114, issued Jun. 16, 2009, describes a wavelength conversion-based multicolor illumination device which employs an excitation light source and a multi-segmented moving plate having wavelength conversion materials (e.g. phosphors). The exciting light source is a light emitting diode or a laser diode emitting in the UV and/or blue region. Each segment of the moving plate contains a different wavelength conversion material or no wavelength conversion material. The plate is supported to move so that different segments are exposed to the excitation light at different times. When the plate moves, light of different colors is generated sequentially in time by the different wavelength conversion materials in different segments of the plate. This multicolor illumination device is useful in a projector system having a microdisplay imager for image display.
Chinese patent application publication CN 101592308A, published Dec. 12, 2009, describes a wavelength conversion-based multicolor illumination device which employs two light sources. The first light source emits an excitation light (e.g. blue or UV) for exciting wavelength conversion materials. The excitation light is introduced onto a rotating wheel which includes multiple segments each carrying a wavelength conversion material. The light from second light source (blue or red) is combined with the converted light from the wavelength conversion material by a dichroic filter which is located downstream from the wavelength conversion material. The second light source can be controlled to turn on and off; for example, it may be turned on only when the rotating wheel is rotated to near a boundary of two segments. This system is designed to solve the problem of spoke light associated with the rotating wheel. Spoke light refers to the undesirable mixing of different color lights occurring at the boundary of two segments of the wheel due to scattering of the converted light and/or other factors.
Chinese patent application publication CN 101858496A, published Oct. 13, 2010, describes a wavelength conversion-based multicolor illumination device that employs two light sources of different colors. The two light sources, one emitting a blue light and the other emitting a UV light, are both disposed before the wavelength conversion material. The blue and UV lights are combined by a light combination element and introduced onto a rotating wavelength conversion element. The wavelength conversion element has multiple segments carrying different wavelength conversion materials, such as red and green phosphors, as well as a clear segment that does not carry any wavelength conversion material but transmits the blue light. Both the UV light and the blue light are used for exciting the wavelength conversion materials. When the clear segment is rotated into the path of the incident light, the UV light source is turned off, and only the blue light is transmitted through the clear segment to produce a blue output light. When the segments carrying wavelength conversion materials are rotated into the path of the incident light, both the blue and UV light sources are turned on to excite the wavelength conversion materials. A sensor is provided to sense the position of the rotating wavelength conversion element and generate a signal for controlling the turning on and off of the UV light source.